1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly a semiconductor device which has a means for preventing data storage capabilities from being lowered and also preventing a wiring film from being increased in resistance or broken under compressive stresses that are imposed on a semiconductor chip when it is sealed in a resin case.
2. Description of the Prior Art
FIG. 1 of the accompanying drawings shows a conventional semiconductor device.
As shown in FIG. 1, the conventional semiconductor device includes a lead frame die pad a, leads b, a semiconductor chip c attached to the die pad a through an adhesive layer d by the die bonding process, connecting wires e connecting the electrodes of the semiconductor chip c to the leads b, and a resin case f which encases and seals the semiconductor chip c.
There are strong demands for reducing the size of circuit components and increasing the level of integration in semiconductor devices, particularly semiconductor memories. If the semiconductor device shown in FIG. 1 is designed to meet such demands, however, compressive stresses are developed in the semiconductor chip c upon shrinkage of the resin of the resin case that seals the semiconductor chip c. More specifically, when the semiconductor chip c is sealed in the resin case f, the temperature of the resin is first high, and then gradually decreases down to normal temperature. The resin and the semiconductor chip c, which is made of silicon, have widely different thermal shrinkage factors. In fact, the thermal shrinkage factor of the resin is much larger than that of the semiconductor chip c. As a result, compressive stresses are developed in the semiconductor chip c when it is sealed in the resin case f.
The developed compressive stresses tend to deteriorate the crystal properties of the semiconductor chip c. Therefore, the compressive stresses adversely affect the circuit components of the semiconductor chip c, and increases the leak currents across junctions which are reverse-biased. Particularly, if the semiconductor device comprises a semiconductor memory, then the developed compressive stresses are liable to lower the data storage capabilities thereof and degrade the metal of its wiring film, thus increasing the resistance thereof or breaking the wiring film itself.
The above problems do not manifest themselves insofar as the circuit components, such as memory cells of the semiconductor memory, are comparatively large and the wiring film is comparatively thick and wide. However, the problems cannot be ignored if the circuit components, e.g., such as memory cells, are smaller and the wiring film is thinner and narrower.